Obesity and physical inactivity have reached epidemic proportions, resulting in increased rates of chronic disease, premature death, and substantial health care costs. Excess weight is even more prevalent in populations with serious mental illnesses (SMI), in part due to medication- induced weight gain and social disadvantage. Since individuals with SMI often have cognitive deficits, specialized approaches are required to help people manage their weight. Researchers have found that specialized in-person interventions focused on diet and activity can help individuals with SMI manage their weight. However, these evidence-based practices have not been widely disseminated. Barriers to the use of these interventions include reluctance of individuals to participate in groups, difficulty finding transportation for frequent visits to clinics, a shortage of trained clinicians, and inadequate clinician time to provide the interventions. It is likely that these barriers can be addressed with a web-based weight intervention that is tailored for individuals with SMI. Specialized web-based approaches have been studied and found to be effective in this population, and can deliver content that is intensive and engaging with minimal requirements for clinician time. Objectives: The investigators on this proposal recently developed a prototype web-based system, called "Help-MI" (Health eLearning for Persons with Mental Illness), that provides limited diet education to individuals with SMI. The current project extends and evaluates this Help-MI system. The project's objectives are to: 1) build on the Help-MI prototype to develop a comprehensive web-based system that delivers an evidence-based weight management program that is focused on diet and activity, and that meets the needs of individuals with SMI;2) evaluate the effectiveness, in individuals with SMI, of Help-MI compared with a control group;and, 3) characterize, from the perspective of individuals with SMI, the strengths, weaknesses, and barriers to the use of Help-MI. Methods: This is a randomized, controlled trial of 90 individuals with SMI at a community mental health center who are overweight and prescribed medications that have weight gain as a common side-effect. Participants are assigned to Help-MI or a comparison group. Research assessments occur at baseline, 3, and 6 months. Changes in outcomes are compared over time between the two groups. Significance: By losing weight, individuals with mental illness can decrease their risk for medical problems, and improve their quality of life and life expectancy. A web-based system that helps individuals lose weight could be feasible to disseminate broadly at medical centers, clinics, and community based programs in both rural and urban areas. PUBLIC HEALTH RELEVANCE: Obesity and physical inactivity have become serious problems for individuals with mental illness, resulting in increased rates of chronic disease, premature death, and substantial health care costs. Although in-person psychoeducational interventions help individuals with mental illness manage their weight, these interventions are often not used because they require frequent travel to treatment programs and substantial time from clinicians. This project addresses these barriers by developing and evaluating the effectiveness of a web-based computer system that is focused on diet and exercise education, and designed to help individuals with mental illness manage their weight.